It may be an illusion, but I feel that since last year, more people talk about MABR in the water circle.

I only started to learn about MABR in 2016. At that time, because of work, I had the honor to listen to people from Fluence at IFAT in Munich introducing the MABR process. At that time, Fluence was also called Emefcy (homonymous M-F-C, indicating that this company has something to do with microbial fuel cells). At that time, I felt that the technology was very powerful, but because of commercial reasons, I didn't have the opportunity to introduce the technology. Now that the conditions permit, I would like to introduce the MABR process in two phases. Today I will first talk about the past and present of MABR.

　　

Author: Farmer in Wa Village

What is MABR?

MABR, the full name of Membrane Aeration Bioreactor, is membrane aeration bioreactor. As the name implies, it is a biological process that uses membranes for aeration, but don't get me wrong. The so-called membrane aeration does not refer to microporous aeration; MABR is an upgraded version of the traditional activated sludge process-it can be based on the existing tank capacity. On the other hand, more sewage can be treated with less oxygen transfer energy consumption.

How does it do it?

The salesman who sells the MABR process may tell you: "We have a self-developed breathable membrane that transmits oxygen to the biofilm adhered to the breathable membrane. Like the human lung, this is a breathable membrane. ."

Don't understand sales? Let's review its history first.

The budding period of MABR

The research on the MABR process can be traced back to the 1960s. The famous F. J. Ludzack and Morris Ettinger used breathable plastic film for oxidation in 1960. They could already see the growth of biofilm on the plastic film.

Ludzack and Ettinger et al.'s 1960 paper screenshots|Source: jstor

For some reason, research in this area was silent for nearly 30 years. It was not until 1978 that related research was reproduced-the team of Professor Charles Jenkins of West Virginia University published an article entitled "Pure oxygen fixed film reactor" in the Journal of the Environmental Engineering Division. They used Teflon capillary tubes to make breathable membranes and synthetic sewage for experiments, and the results seemed to be good-even under high organic load conditions, the removal rate of BOD was as high as 90%. But they called the designed reactor MABR at the time, but Aerobic Media Trickling Filter. I personally guess that this is because the biological trickling filter is more familiar, after all, it was one of the most common sewage treatment processes in the first half of the last century.

Why did they think of using Teflon capillaries for experiments? It is said that they were inspired by an article in "Science" in 1972-people in the American medical community used artificial capillaries for in vitro cell culture. I turned over the original text, the principle is indeed very similar. Does this mean that many innovations in the sewage industry need to hold the thighs of biology and chemistry?

Schematic diagram of Science in vitro cell culture article | Source: Sciencemag.org

Road to pilot test

But after that, MABR research seems to be dropped again. It wasn't until 1986 that Canadian Dr. Pierre Côté and several other colleagues published the following article in the Journal of Membrane Science, that MABR research was put on the right track again.

The beginning of the paper published by Dr. Pierre Côté and his colleagues in 1986 | Source: jstor

The following is a schematic diagram of the hollow fiber membrane module he drew (it was not easy to draw a picture back then): Because oxygen is transferred from one side of the membrane to the other side of the membrane through diffusion, no bubbles will be generated. So they called it bubble-free aeration at the time.

Dr. Côté's hollow fiber membrane oxygen transfer schematic diagram | Source: JSTOR

But the Canadian went to work on something more important-he went to a great company to develop ultrafiltration membranes. This company is called ZENON Enviroment. He became the company's CTO in 1998 until it was later acquired by GE.

Dr. Pierre Côté and Professor Michael Semmens

Fortunately, at that time, Dr. Côté was not the only one who was tinkering with this stuff, and Professor Michael Semmens of the University of Minnesota was also doing related research. In 1999, his team published an article titled "Pilot-Plant Treatment of a High-Strength Brewery Wastewater Using a Membrane-Aeration Bioreactor" in the journal Water Environment Research. The term MABR is officially available and entering the pilot test stage.

A review of membrane reactors written by the Semmens team | Adapted by a farmer in Wa Village, reference: JSTOR

In the same year, the team of Professor Eoin Casey from the University of Dublin in Ireland also reported on the research progress of membrane oxygen transfer materials in the international journal "Biotechnology and Bioengineering", and also used the abbreviation MABR. The only difference is that the A here refers to aerated, not aeration. Please understand the difference.

Professor Eoin Casey and his MABR membrane module | Source: UCD

The core competitiveness of MABR

After reading the history, we return to the original question: Why is the energy consumption of MABR process much lower than other processes?

I drew the following picture to explain:

The upper part of this picture is the biofilm model that most university teachers and professors will introduce to you. The black part is a variety of carriers. The biofilm formed on the carrier can be roughly divided into an aerobic layer and an anoxic layer. (If the film is thick enough, the anaerobic zone is not excluded), then the mass transfer and diffusion of organic matter and ammonia nitrogen and other pollutants are carried out from the side of the mixed liquid to the side of the carrier. Because oxygen is driven into the mixed liquid through the aeration sheet/disk, the diffusion of dissolved oxygen is in the same direction as BOD/ammonia nitrogen. In the biofilm formed in this way, the aerobic layer is on the side of the sewage and the hypoxic zone is on the side close to the biofilm.

The lower part of the picture is a model of MABR membrane that most students have never heard of in college. The difference between it and the biofilm is that the positions of the aerobic and hypoxic layers of the biofilm are just reversed! Why is this? Because oxygen is transmitted from the inside of the membrane to the outside of the membrane through the gas permeable membrane, because of its mass transfer and diffusion effect. The direction of the BOD/Ammonia Nitrogen is just the opposite!

This means:

1. The actual residence time of oxygen is greatly extended, and the oxygen-containing gas in the membrane will not be driven out of the mixed liquid due to the buoyancy of water;

2. Air can be delivered at low pressure, because the air does not need to overcome the hydrostatic pressure to pass through the hollow fiber membrane (the self-breathing membrane in sales means that it can operate under atmospheric pressure);

3. Greatly reduce the aeration rate, because the dissolved oxygen transfer efficiency (OTE) of the MABR reactor can be as high as 90% (. (SUEZ senior engineer Jeff Peeters said that the OTE of MABR is four times that of microporous aeration)< /p>

4. Nitrification and denitrification can be completed in a reaction tank!

MABR's nitrogen transformation schematic diagram | Design: Farmer in Wa Village

The fourth point is that I didn't notice when I first came into contact with MABR. I just thought it was a low-energy aeration technology. Later I learned about the advantages of this biofilm structure-in traditional biological In membrane or suspension systems, oxygen is the limiting factor. Especially when the dissolved COD is high, nitrifying bacteria will often lose to heterotrophic bacteria in the battle for dissolved oxygen. In order to provide more residence time for nitrifying bacteria, it is often To design reflow. However, in the MABR system, oxygen is no longer a limiting factor, and nitrifying bacteria do not need to compete with heterotrophic bacteria for oxygen. Nitrification and denitrification reactions are carried out on the inner and outer sides of the biofilm (as shown in the figure above). Need to reflow. In this system, denitrification does not require an additional carbon source, which means that nitrate nitrogen can be used to oxidize and utilize BOD in sewage. More importantly, this provides a good control mechanism for mainstream anammox. Many teams are conducting research in this area, including the team of Professor Glen Daigger from the University of Michigan, the former chairman of the IWA International Water Association.

Comparison of oxygen transfer efficiency of various aeration technologies | Data source: Stenstrom & Rosso+Black & Veatch, View production: Wa village farmer

Core issues

You may ask: What is said so well, why did MABR not have any engineering cases from 1999 to 2015?

As for this question worth hundreds of millions of dollars, the editor is obviously unable to give an official answer, but I personally think that one of the reasons is that the developers of the MABR process need more time to understand and build the growth model of the MABR biofilm. How can water investors have the confidence to pay for it without seeing a controllable biofilm?

Comparison between MABR membrane and traditional biomembrane | Production: Wa Village Farmer

Canada's sewage modeling company inCTRL Solutions seems to have found the mystery: on the webinar last September, they shared some of the latest analysis data. As shown in the figure below, after the thickness of the MABR film exceeds 0.5μm , The concentration of nitrate nitrogen/nitrite nitrogen in the effluent can be lower than 5mg/L, but as the film thickness further increases, the removal efficiency of ammonia nitrogen will decrease. This picture is of great significance to the MABR process engineers, which means that they need to find a suitable balance point based on the inlet water concentration and the outlet water standard.

MABR film thickness is exquisite | Source: Inctrl solutions

The difficult road to commercialization

After more than ten years of accumulation, MABR's business seems to have increased after 2013:

In 2013, Oxymem, a spinout company of the University of Dublin, claimed to be the first to develop a commercial hollow fiber membrane for MABR, and in June 2014 it won its first customer-British Enisca used Oxymem's MABR technology in a landfill in Ireland The district builds a sewage treatment system.

In 2015, the then GE Water Treatment Company also launched the MABR commercial membrane, named ZeeLung™. Remember Dr. Pierre Cote? Many of ZeeLung's technology patents are related to him, but in 2009 he had already started his own company.

In 2016, a new generation of flat MABR film from Emefcy of Israel was launched on the market. It is said that the company was established as early as 2008 and has also received investment from GE. They claimed to have created breathable membrane technology at the time, but encountered blockage problems in subsequent operations, so they have been optimizing since then. The new 2016 model is an optimized product.

Comparison of the appearance of components of the three major MABR manufacturers | Source: B&V

But in the past few years, these three companies have been merged or reorganized one after another:

In March 2017, GE Water Treatment Company was acquired by SUEZ;

In July 2017, Emefcy and RWL merged to form Fluence;

In December 2019, DuPont acquired Oxymem.

After the reorganization of these three companies, it seems that they have been given more resources: in September last year, Oxymem won the expansion project of the Worcestershire sewage treatment plant of the British water company Severn Trent, and won GWI's "Technology Breakthrough Company of the Year Award" ". In other words, Professor Semmens of the University of Minnesota became a consultant for the company after his retirement.

The largest MABR system installation site in the UK | Source: Oxymem

After obtaining the ZeeLung membrane technology, SUEZ first published the pilot test results of the Chicago O'brien wastewater treatment plant in the journal Water Science & Technology of the IWA International Water Association, which showed a stable oxygen transmission rate, and most of the oxygen Used for nitrification. After demonstrating the energy saving and capacity expansion potential of MABR for existing or A2O wastewater treatment plants with the help of authoritative journals, SUEZ won the upgrade and expansion project of the Hespeler wastewater treatment plant in Canada in August last year and is expected to start production this year. It is said that this will be the largest MABR case at present, with a processing capacity of about 10,000m³/day.

O'brien Wastewater Treatment Plant

Compared with the previous two companies, Fluence is more active in expanding the market in China. It has already cooperated with Gezhouba, Qingshuiyuan and many other companies to accumulate cases of decentralized sewage treatment. It seems that it has to take the road of encircling the city from the countryside. In addition, their MABR case in the Mayan Zvi wastewater treatment plant in Israel has also been recognized and endorsed by the design consulting giant Black & Veatch.

Fluence's 300m³/day project in Luoyang, Henan | Source: Fluence

The orders of the above three companies seem to mostly come from the demand for in-situ expansion of sewage plants or energy saving and consumption reduction. This reflects that the market's response to MABR is still cautious and rational. On the other hand, it shows that this is the advantage of MABR. It also gives MABR manufacturers a valuable opportunity to prove the superiority of their process.

Most of the current renovation projects are in a modular manner, putting multiple membrane modules into the anoxic zone of the existing sewage plant, where simultaneous nitrification and denitrification are completed in this area, and the reflux bypass can be eliminated. If the long-term data of these projects is convincing, it is estimated that the prospects of MABR are worth looking forward to.

MABR process flow chart | Source: Youtube@fluence

From 1960 to 2020, the journey of MABR has been tortuous enough. Finally, I want to share a picture, which is a trend chart of MABR performance shared by Dr. Leon Downing, Chief Process Engineer of Black & Veatch. The editor personally thinks that the future sewage treatment plant will have a place for MABR. After all, in the sewage treatment industry, no matter how good the technology seems, it will take about ten years to usher in its own spring.

The development trend of MABR | Source: Leon Downing

The above are purely personal opinions. Please correct me for any improprieties.

Reference material

1.https://www.jstor.org/stable/25045302?seq=1

2.https://www.sciencedirect.com/science/article/abs/pii/S0376738800808625

3.https://www.linkedin.com/in/michael-semmens-225446b/

4.https://cca-reports.ca/experts/pierre-cote/

5.https://www.jstor.org/stable/25034243?seq=1

6.https://cedb.asce.org/CEDBsearch/record.jsp?dockey=0008217

7.https://science.sciencemag.org/content/178/4056/65

8.https://www.ucd.ie/chembioeng/t4media/Eoin-Casey.pdf

9.https://www.linkedin.com/in/pierre-c%C3%B4t%C3%A9-5291a226/?originalSubdomain=ca

10.https://www.semanticscholar.org/paper/Where-did-the-bubbles-go-How-to-reduce-the-energy-Vale-Casey/6ce1e34371546ee81fd9c4734bafdd5939b9f643

11.https://envbiotech.engin.umich.edu/projects/brettproject/

12.http://www.newea.org/wp-content/uploads/2017/02/NEWEA17_Session09_KMartin.pdf

13.https://iwaponline.com/wpt/article/12/4/927/38672/Demonstration-of-innovative-MABR-low-energy